Easter Island was once home to lush palm forests. Over time, however, the humans who settled there depleted the island’s resources, leading to wars among clans that doomed the population.

Their legacy, the giant stone sculptures called moai, have drawn intense interest and fascination ever since Europeans discovered them in 1722. One theory posits that the early Polynesians who settled on the island, also known as Rapa Nui, cut down trees for logs to roll the statues from their quarries to their overlook positions. Competition among clans led to ever bigger moai and, ultimately, to the destruction of the forest.

Some researchers doubt that such logging could have devastated the island, especially if the statues “walked” into position, as Polynesian mythology holds. Indeed, scientists published a paper last month showing just how a moai could have been walked with a series of ropes pulled by dedicated volunteers.

Their demonstration supports other theories for the disappearance of the Easter Islanders, such as the hunting to extinction of sea birds, whose droppings nourished the forest. This and other explanations are summed up in this sneak-peek NOVA clip. The full program premieres on Wednesday, November 7 at 9 P.M. Eastern on PBS.